Indwelling ureteral catheter stents or drainage tubes have been used to bypass ureteral obstructions or ureterovaginal fistulas and to achieve and to maintain urinary drainage. In the past, stents made of straight lengths of open end tubing have been used for this purpose and have provided good drainage for sustained periods of time. However, the use of such tubing has not been completely satisfactory. For example, in some instances, the tubing has migrated and in others it has been expelled.
Various attempts have been made to produce stents which do not have the problems which accompany the use of such tubing. For example, stents have been designed which are closed at one end to facilitate passage into a body passage and which have at the other end a flange to make upward migration of the stent less likely. Another approach has been to provide the body of the stent with sharply pointed barbs which are designed to prevent downward migration and expulsion. However, such barbs increase the diameter of the stent making it more difficult to insert and in some instances can cause the stent to migrate outside the bladder.
In Finney U.S. Pat. No. 4,212,304 issued July 15, 1979 and Finney U.S. Pat. No. 4,307,723 issued Dec. 29, 1981, ureteral stents are disclosed which have hooks at each end and which are surprisingly effective in preventing migration and expulsion. The patented stents are widely accepted because they can be easily introduced both endoscopically and during open surgery. However, like most other commercially available stents it is difficult to maneuver them past obstructions in the ureter.
In Densow U.S. Pat. No. 4,610,657 a stent is disclosed which has a hook at each end, a lumen and a reduced opening at the proximal end. The guidewire system disclosed for use with the stent comprises two separate guidewires. One of the wires is the pusher wire. It is smaller in diameter than the lumen of the stent but has a proximal end which is larger than the reduced opening at the proximal end; it is used to push the stent in place when no obstructions are encountered. The other wire is used when an obstruction is encountered. It is smaller in diameter than the first wire and the reduced opening in the stent. When an obstruction is encountered the stent and the pusher wire are withdrawn and the pusher wire is removed. The smaller diameter wire is inserted in the lumen of the stent and the stent and wire reinserted; the leading end of the smaller wire is then advanced out the reduced opening in the proximal end and maneuvered past the obstruction. The stent is then run over the guidewire past the obstruction. Once the leading end of the stent is past the obstruction, the stent is pushed into place with the pusher wire or a stent pusher.
It would be advantageous to have a guidewire system that could be used to either advance a stent in the normal fashion or to guide it past an obstruction without having to withdraw the stent from the patient to replace the guidewire or having to withdraw the guidewire from the stent before it is in place.